CMOS Infrared Detector with Integrated Sensing Structure
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Solution Overview
Problem
Current infrared detectors face process incompatibility and performance issues due to the combination of CMOS measuring circuits and MEMS infrared sensing structures, leading to incomplete sacrificial layer release, limited material selection, inconsistent resonant cavity height, and low production capacity, which restricts performance consistency and miniaturization.
Innovation Solution
An infrared detector is developed using a CMOS process that integrates both the CMOS measuring circuit system and CMOS infrared sensing structure, featuring a sealed release isolation layer, thermal-sensitive dielectric layers, and a resonant cavity, allowing for direct fabrication on the CMOS production line, eliminating process compatibility issues and enabling high-yield, low-cost, large-scale production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If MEMS process is used to fabricate infrared sensing structure, then infrared detection function is achieved, but process compatibility with CMOS is poor and production capacity is low
Solution Approach 1:
The patent merges the MEMS infrared sensing structure fabrication with the CMOS measuring circuit fabrication into a single integrated CMOS process flow. The infrared sensing structure is fabricated directly on the CMOS measuring circuit system using CMOS-compatible materials and processes, eliminating the need for separate MEMS processing steps and achieving full process compatibility while maintaining infrared detection functionality.
Solution Approach 2:
The CMOS process is made universal to perform both the fabrication of measuring circuits and infrared sensing structures. By using CMOS-compatible sacrificial layers (such as silicon oxide instead of polyimide) and CMOS-compatible materials for the infrared sensing structure, the same fabrication platform serves multiple functions, enabling large-scale production with high yield rates.
2Ease of manufacture
If polyimide is used as sacrificial layer in MEMS process, then release structure is formed, but release is incomplete and affects vacuum level
Solution Approach 1:
The patent replaces the polyimide sacrificial layer with a silicon oxide sacrificial layer that is completely removable. The silicon oxide layer serves as a temporary structure during fabrication that can be completely released through selective etching processes, leaving no residual material that would contaminate the vacuum environment or affect the final device performance.
Solution Approach 2:
The patent changes the material parameter of the sacrificial layer from polyimide to silicon oxide, which has different etch selectivity properties. This material substitution enables complete release of the sacrificial layer through CMOS-compatible etching processes, achieving both ease of manufacture and precise control of the vacuum level in the final device.
3Ease of manufacture
If polyimide sacrificial layer is used, then structure release is attempted, but resonant cavity height becomes inconsistent
Solution Approach 1:
The silicon oxide sacrificial layer is designed as a completely removable temporary structure with uniform thickness control. Its consistent removal through selective etching ensures that the resonant cavity height is uniform across all devices, solving the height inconsistency problem that occurs with polyimide release.
Solution Approach 2:
The silicon oxide sacrificial layer is deposited with precise thickness control before the resonant cavity structure is formed. This preliminary action ensures that the cavity height is predetermined and consistent, and the uniform etching of the sacrificial layer maintains this consistency throughout the release process.
4Reliability
If MEMS process is used, then infrared sensing structure is fabricated, but production capacity is low and cost is high
Solution Approach 1:
The patent combines the fabrication of infrared sensing structures with the CMOS measuring circuit fabrication into a single integrated process flow. This merging allows both structures to be fabricated simultaneously on the same wafer using the same CMOS fabrication lines, dramatically increasing production capacity and reducing costs while maintaining the required infrared sensing functionality.
5Reliability
If MEMS process is used, then infrared detector is fabricated, but chip miniaturization is limited
Solution Approach 1:
The integration of the infrared sensing structure directly on the CMOS measuring circuit system eliminates the need for separate packaging and interconnection structures required by traditional MEMS approaches. This merging enables significant chip miniaturization while maintaining full infrared detector functionality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution achieves higher detection sensitivity, longer detection distance, better performance consistency, and miniaturization of chips, with improved control precision and industrial mass production capabilities, addressing the limitations of the MEMS process.
Implementation Method 1
The thermal-sensitive dielectric layer includes a thermal-sensitive material with a temperature coefficient of resistance greater than a predetermined value. The thermal-sensitive dielectric layer is configured to convert a temperature change corresponding to infrared radiation absorbed by the thermal-sensitive dielectric layer into a resistance change
Implementation Method 2
The thermal-sensitive dielectric layer includes a thermal-sensitive material with a temperature coefficient of resistance greater than a predetermined value
Implementation Method 3
The metal interconnect layer at least includes a reflecting layer and an electrode layer. The CMOS infrared sensing structure includes a resonant cavity formed by the reflecting layer and the thermal-sensitive dielectric layer
Implementation Method 4
The CMOS infrared sensing structure includes a resonant cavity formed by the reflecting layer and the thermal-sensitive dielectric layer
Data Source
AI summary
An infrared detector based on a CMOS process is provided. A CMOS measuring circuit system (1) and a CMOS infrared sensing structure (2) in the infrared detector are both fabricated using the CMOS process, and the CMOS infrared sensing structure (2) is directly fabricated above the CMOS measuring circuit system (1); a CMOS fabricating process of the CMOS infrared sensing structure (2) comprises a metal interconnection process, an interconnect via process and an RDL process, the CMOS infrared sensing structure (2) comprises at least two metal interconnect layers, at least two dielectric layers and a plurality of interconnect through holes, the dielectric layer at least comprises one sacrificial layer and one thermal-sensitive dielectric layer, and the thermal-sensitive dielectric layer comprises a thermal-sensitive material with a temperature coefficient of resistance greater than a predetermined value; and the CMOS infrared sensing structure comprises a resonant cavity formed by a reflecting layer (4) and the thermal-sensitive dielectric layer, a suspended micro-bridge structure for controlling heat transfer and a columnar structure (6) having electrical connection and supporting functions. Problems of low performance, low pixel scale and low yield of a conventional infrared detector based on a MEMS process are solved, and the performance of the infrared detector is optimized.